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Diffstat (limited to 'tests/codegen/align-offset.rs')
-rw-r--r-- | tests/codegen/align-offset.rs | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/tests/codegen/align-offset.rs b/tests/codegen/align-offset.rs new file mode 100644 index 00000000000..7c7660c5a55 --- /dev/null +++ b/tests/codegen/align-offset.rs @@ -0,0 +1,78 @@ +// compile-flags: -O +// min-llvm-version: 15.0 (because we're using opaque pointers) +// ignore-debug (debug assertions in `slice::from_raw_parts` block optimizations) + +#![crate_type = "lib"] + +// CHECK-LABEL: @align8 +#[no_mangle] +pub fn align8(p: *const u8) -> bool { + // CHECK: ret i1 true + p.align_offset(8) < 8 +} + +#[repr(align(4))] +pub struct Align4([u8; 4]); + +// CHECK-LABEL: @align_to4 +#[no_mangle] +pub fn align_to4(x: &[u8]) -> bool { + // CHECK: ret i1 true + let (prefix, _middle, suffix) = unsafe { x.align_to::<Align4>() }; + prefix.len() < 4 && suffix.len() < 4 +} + +// CHECK-LABEL: @align_offset_byte_ptr(ptr{{.+}}%ptr) +#[no_mangle] +pub fn align_offset_byte_ptr(ptr: *const u8) -> usize { + // CHECK: %[[ADDR:.+]] = ptrtoint ptr %ptr to [[USIZE:i[0-9]+]] + // CHECK: %[[UP:.+]] = add [[USIZE]] %[[ADDR]], 31 + // CHECK: %[[ALIGNED:.+]] = and [[USIZE]] %[[UP]], -32 + // CHECK: %[[OFFSET:.+]] = sub [[USIZE]] %[[ALIGNED]], %[[ADDR]] + + // Since we're offsetting a byte pointer, there's no further fixups + // CHECK-NOT: shr + // CHECK-NOT: div + // CHECK-NOT: select + + // CHECK: ret [[USIZE]] %[[OFFSET]] + ptr.align_offset(32) +} + +// CHECK-LABEL: @align_offset_word_slice(ptr{{.+}}align 4{{.+}}%slice.0 +#[no_mangle] +pub fn align_offset_word_slice(slice: &[Align4]) -> usize { + // CHECK: %[[ADDR:.+]] = ptrtoint ptr %slice.0 to [[USIZE]] + // CHECK: %[[UP:.+]] = add [[USIZE]] %[[ADDR]], 31 + // CHECK: %[[ALIGNED:.+]] = and [[USIZE]] %[[UP]], -32 + // CHECK: %[[BOFFSET:.+]] = sub [[USIZE]] %[[ALIGNED]], %[[ADDR]] + // CHECK: %[[OFFSET:.+]] = lshr exact [[USIZE]] %[[BOFFSET]], 2 + + // Slices are known to be aligned, so we don't need the "maybe -1" path + // CHECK-NOT: select + + // CHECK: ret [[USIZE]] %[[OFFSET]] + slice.as_ptr().align_offset(32) +} + + +// CHECK-LABEL: @align_offset_word_ptr(ptr{{.+}}%ptr +#[no_mangle] +pub fn align_offset_word_ptr(ptr: *const Align4) -> usize { + // CHECK: %[[ADDR:.+]] = ptrtoint ptr %ptr to [[USIZE]] + // CHECK: %[[UP:.+]] = add [[USIZE]] %[[ADDR]], 31 + // CHECK: %[[ALIGNED:.+]] = and [[USIZE]] %[[UP]], -32 + // CHECK: %[[BOFFSET:.+]] = sub [[USIZE]] %[[ALIGNED]], %[[ADDR]] + + // While we can always get a *byte* offset that will work, if the original + // pointer is unaligned it might be impossible to return an *element* offset + // that will make it aligned. We want it to be a `select`, not a `br`, so + // that the assembly will be branchless. + // CHECK: %[[LOW:.+]] = and [[USIZE]] %[[ADDR]], 3 + // CHECK: %[[ORIGINAL_ALIGNED:.+]] = icmp eq [[USIZE]] %[[LOW]], 0 + // CHECK: %[[OFFSET:.+]] = lshr exact [[USIZE]] %[[BOFFSET]], 2 + // CHECK: %[[R:.+]] = select i1 %[[ORIGINAL_ALIGNED]], [[USIZE]] %[[OFFSET]], [[USIZE]] -1 + + // CHECK: ret [[USIZE]] %[[R]] + ptr.align_offset(32) +} |